Until recently, chloro, fluoro carbons (CFCs) were used extensively for refrigeration. However, upon discovery of their adverse environmental effects, particularly with respect to depletion of the ozone layer, CFCs have become disfavored, and new refrigerants have been developed. In particular, HCFCs and HFCs have come into mandatory use. While these refrigerants are chemically similar to CFCs and are not totally environmentally benign, they are much less harmful to the ozone layer.
In conjunction with HCFC and HFC refrigerants, lubricants are required for refrigeration apparatus maintenance. In the past, with CFC refrigerants, mineral oil or simple alkyl benzenes were used as lubricants. When HCFCs or HFCs became mandated, it was found that the old lubricants were not compatible with either HCFCs or HFCs. In addition, corrosion inhibitors and antioxidants started to be used, further extending the requirements of the lubricants. To satisfy these requirements, polyol esters and poly-alkylene glycol (PAG) lubricants were developed and have become the standard lubricants for the new HCFS. Such lubricants are typically used in amounts in the range of 1% by weight relative to the HCFC or HFC refrigerants. The particular formulation of an HCFC/HFC lubricant is often proprietary. The lubricants may vary widely in both cost and effectiveness. Accordingly, a manufacture of refrigeration apparatus may require that the apparatus be maintained using a particular type of lubricant when recharging the apparatus with refrigerant, or a service contract may call for a particular lubricant to be used in recharging apparatus.
Furthermore, refrigeration apparatus is very expensive to install. Lubricants for old (CFC) systems are incompatible with the new (HCFC/HFC) systems; thus a need to tag lubricants for the new systems and be able to identify any dilution of new lubricants with old lubricants.
In some cases, use of old CFC refrigerants are permitted in older refrigeration systems which cannot utilize the newer HCFC/HFC systems. This means that the older CFC refrigerants may be available for a limited time. While CFC refrigerants should not be used in the newer refrigeration systems designed for HCFC/HFC use, the older CFC refrigerants are much cheaper than the HCFC/HFC refrigerants, and there may be a strong temptation to misuse CFC refrigerants by recharging a HCFC- or HFC-compatible system with CFC refrigerants. To prevent this, CFCs might be tagged with an identifiable marker. If misused in an HCFC- or HFC-compatible system such markers will be mixed in the residual polyol ester or PAG lubricants from the initial HCFC/HFC charge, from which they can be identified.
It would be desirable to have a simple, straight-forward test to determine whether a particular lubricant has, in fact, been used when charging or recharging refrigeration apparatus. The lubricants, however, while sufficiently different from each other to function with varying effectiveness, are sufficiently similar as not to be easily distinguished by simple chemical tests.
It is possible to dye lubricants; however, fluorescent dyes are generally added to refrigeration systems for leak detection purposes, and it is therefore undesirable to add a second dye which could mask the fluorescence.
Petroleum fuels are often tagged for the purpose of identifying grades or tax category. Markers for the tagging of petroleum fuels are described for example, in U.S. Pat. Nos. 4,209,302, 4,904,765, 5,156,653, 5,205,840,and 5,252,106, the teachings of each of which is incorporated herein by reference. The markers used for tagging petroleum fuel are intended to be silent, i.e., provide no significant coloration to the petroleum fuel. They may be naturally colorless or insignificantly colorful at the concentrations used in tagging petroleum, or they may be used in conjunction with dyes which mask any color the marker may impart. Such markers, however, are extractable with aqueous solutions, which depending upon the marker may be acidic, basic, and/or may contain an alcohol. The markers also are capable of undergoing a chromophoric change to produce an intense color, such as by reaction with the acid or base of the aqueous solution or with another chemical reagent which may be included in the extracting aqueous solution or subsequently added thereto.
Herein, a method is provided for tagging and identifying refrigeration lubricants using silent markers, such as those in the patents referenced above.